Test is an important step in the manufacture of semiconductor devices. The automatic test equipment (ATE) employed to carry out this task comprises sophisticated electronics capable of sending test signals to, and capturing output signals from, one or more devices under test (DUTs). This back and forth flow of signals is orchestrated by ATE channel hardware, typically referred to as “channels”. There is often a one-to-one correspondence between the ATE channels and DUT I/O pins.
Until recently, ATE channels were predominantly DC-coupled to the device-under-test. DC-coupling allows for both DC and AC test signals to propagate between the ATE and the DUT. However, because of the technology differences between the DUT and the tester pin electronics drivers, significant DC offsets were common. DC offsets can undesirably affect accuracy in the application and detection of signals with defined logic levels. This problem was often solvable by merely adjusting threshold voltage levels with the conventional ATE drivers so that the DC offset at the driver matched that of the DUT receiver.
While the DC-coupling scheme worked fine for its intended low-speed applications, modern communications devices deal with very fast signals having very small voltage swings. Unlike the older (and slower) conventional pin electronics drivers optimized for relatively large voltage swings, the ATE drivers implemented to interface with high-speed communications devices have limited DC offset adjustment capability, if any at all. To alleviate this problem, the tester channel may be AC-coupled to the device, removing any DC signal components from the channel signal path.
Recently, semiconductor devices that were typically tested via DC-coupled ATE channels, such as microprocessors, have begun implementing communications technology that benefits from an AC-coupled channel. However, many of the pins of those devices also benefit from a DC-coupled channel. While a high-speed AC data stream may be tested on a conventional DC-coupled channel, a long series of “0”s or “1s” may cause a drift in the DC offset. This has the potential to undesirably affect the tester accuracy.
Consequently, the need exists for an ATE channel architecture that may be reliably and accurately employed for the transmission and reception of broadband signals ranging from DC up to the tens of gigahertz. The hybrid AC/DC-Coupled channel architecture of the present invention satisfies this need.